There exists a known gas pressure actuator that is used, for example, for a device to lift a hood of a motor vehicle, and is extended by a high-pressure gas generated by a gas generator (see, for example, Patent Document 1). The gas pressure actuator includes the gas generator, a body cylinder, and a piston rod. The gas generator is disposed at an end in an axial direction of the body cylinder. The piston rod is lined up with the gas generator in the axial direction so that a piston is slidable along the inner wall of the body cylinder, and the piston rod can protrude from the other end in the axial direction of the body cylinder.
In the gas pressure actuator described above, when the gas generator generates the high-pressure gas, the high-pressure gas acts on a surface of the piston facing the gas generator in the axial direction, and the piston receives a force that presses the piston in the axial direction. When such a pressing force is generated, the piston slides in the body cylinder and is displaced in the axial direction. As a result, the gas pressure actuator is extended in the axial direction.